Can I shoot this gun?

AR/M4 AR Technical Discussion
1

Just got a 16" middie BFH BCM w/ 12" Larue rail in the mail today and it’s nasty.

Primo all the way around.

Had irons and charging handle already. Did NOT; however, have a BCG…For the time being, my father is loaning me one of his that has NEVER been used.

Again, all components are brand new.

For the life of us, neither can remember where he got it from nor the mfg…It’s likely that it’s BCM or LMT; however, it cannot be verified.

The bolt itself is marked with “AJ” on one side and “MP” on the other, which is obviously, a good sign.

Now, he’s got a set of gauges. All he gave me are the GO and NO-GO. Markings are as follows.

223 REM
-GO-
CLY3/9
1.4636"

223 REM

  • NO GO-
    CLY3/9
    1.4666"

First, are these reputable gauges…I’ve heard of Clyburne Gauges. These sound like they may be such.

Two, neither will go into battery. I’m easing the bolt down; however, not removing any spring nor ejector from the bolt.

I utilized the search function; however, am obviously a dumb fuck.
Any help is appreciated.

Thanks

2

Are there relief cuts on the gauges for the ejector? If not, I don’t think you can accurately use those gauges unless you remove the ejector.

3

Unless you have a USGI gauge, you’re going to have to remove the ejector and extractor to check headspace. There’s no point in using .223 gauges on a BCM barrel with a 5.56 chamber. I can think of some companies that call a .223 and 5.56 chamber the same thing, but BCM isn’t one of them.

If it’s a bolt from a known quality source (like BCM or LMT) I’d just shoot the rifle.

4

I am 99% sure that the markings on the bolt are indicative of LMT. None of those gages you have listed would be correct. IMPO.

Having said that. The quality of the upper and BCG are of reliable enough pedigree that I probably wouldn’t worry.

5

Unless they have relief cuts, the only way to check is to strip the bolt and scrub the chamber.

Check by hand, not by trying to shove the assembled bolt/carrier group home.

“Cly” would most likely be Clymer, a first-rate set of gauges.

6

Clymer makes good stuff. Just not applicable to the AR15.

7

no relief cuts on gauges…smooth all the way around. “Clymer”…they’re the ones I’ve heard of.

roger that…thanks for the quick replies all.

any other responses to verify IraqGunz on the markings on the bolt would be magnificent. truly hoping it’s an LMT.

thanks again fellas…

BTW, i sold my LMT Piston upper to fund this upper. Got a Noveske N4 w/ VIS and a DD M4V5 and I think I just wanted something a bit different.

It was basically new, so I only lost about 250.00 in the sell…It was an AMAZING piece and ran like a sewing machine and with very, very, VERY minimal extension wear; however, the damn thing was just HEAVY. Built like a tank but i had yet to stick an optic on it and…well, it was almost as if ol’ man Stoner visited me in my dreams one night and gave me a royal ass kickin’.

DI it is!!!

8

5.56 chamber will close on a .223 nogo gauge so it’s kinda pointless.

9

I have done some snooping. AJ and AC are two known LMT bolt markings. A picture would be great. I believe that they are fairly small and are in standard script.

10

I agree on the LMT bolt. Supposedly the A(letter) is their heat treating proof mark stamp. I have AM and AT marked LMT bolts.

11

Sounds like LMT markings. I have several with similar markings. I can’t access them right now, so I can’t verify.

I wouldn’t sweat it, and just go shoot it.

12

Not that any of the guys that have already posted need any backup/confirmation from me, but I have 8 LMT BCGs, and after checking, at least 2 of them have identical markings.

Regards.

Mark

13

MIL-C-70599A(AR)
3.4.1 Headspace. The headspace shall not be less than
1.4646 inches nor more than 1.4706 inches when measured to the
.330 inch datum diameter on the first shoulder of the chamber.

SAAMI 223 Remington Headspace
1.4636 MIN
1.4736 MAX
@ .330 DIA

As you can see above if the 1.4636 will not close (when properly used) your headspace will be below both 5.56 and 223 Rem spec and I would not recommend firing it. The spec is slightly different BUT, the gauges will properly measure HS in BOTH chambers at the correct diameter on the same angle. Being within 223 Rem spec is much safer than not checking HS because the gauge is not 5.56 spec.

14

Shoot it. But I would get a quality BCG soon as the parts will wear together.

15

Again, thanks for all the replies…too late for a pic now, i’m beat.

to the previous poster, it’s kinda hard to beat an LMT BCG, no???

i think i’m pretty good on the quality of my current BCG; however, this IS obviously assuming it’s an LMT.

i do appreciate the recommendation…i will be picking up an AUTO BCG from BCM ASAP.

i feel like i’m gonna throw some gloves, ear pro and eye pro and go shoot the sumbitch.

16

BTW, no offense to anybody else, but on top of IraqGunz weighing in, it’s pretty cool to have an SME and Todd from Noveske take time to offer their input…Thanks again.

17

Iraw, ur correct. VERY small and the letters are upper case.

Looks exactly like:

AJ

other side

MP

18

billybronco, are you still in VA?

19

I sure am bud…I’m out in New Kent…Actually, Charlie Sodan and I still hang out.

He’s got a shop in a little sporting goods shop on 249 right near my house. Absolutely Outdoors.

You still get by DeGoff’s anymore?

You remember when I brought that damn Kimber back to the shop cuz I was so frustrated with the reassembly process??? Shit, that was close to 12 years ago!